1. Field of the Invention
The present invention relates generally to optimizing implant position during total knee arthroplasty (TKA), and more particularly to a novel method of preoperatively characterizing an individual patient's biomechanic function in order to optimize the orientation of components of a knee prosthesis.
2. Related Art
Software programs which simulate in-vivo functional activities (e.g., LifeMOD™/KneeSIM, a product of LifeModeler®, Inc. San Clemente, Calif.), have been used for the purpose of evaluating the performance of implant designs. Such programs use a three-dimensional, dynamics-oriented, physics-based modeling methodology. While these programs have been used to design implant geometries in the past, the prior art has not utilized such software to fine-tune the anatomical placement of implants (i.e., standard and custom) so that they meet and exceed an individual patient's needs.
Many times in total knee arthroplasty (TKA), poor post-operative patient outcomes are not caused from a poorly-designed prosthesis. Instead, the problem may often stem from a well-designed prosthesis being installed in a less-than-optimal biomechanic position relative to the natural anatomy of the patient in an attempt to get the best anatomic fit. In other words, the probability of revision knee surgery due to pain or abnormal wear may be high even with a well-designed knee-prosthesis, if said prosthesis is misaligned or if said prosthesis is installed without considering the biomechanic effects of prosthetic orientation.
Conventionally, knee prosthetic components are pre-operatively sized and positioned based on static anterior-posterior and/or sagittal X-ray templates in full extension. Range of motion (ROM) and joint stability is assessed with the patient under anesthesia, and so any pain from overstressing or impinging soft tissue that might result from surgery (for example, pain associated with “stuffing the patella” or “stuffing the flexion-extension gap”) cannot be determined until the patient recovers and discovers an unwanted or unnatural post-operative feeling.
The present invention aims to solve the problems encountered in the past by providing alternative preoperative and intra-operative “templating” method steps which give significant weight to soft tissue balancing and patient biomechanic function, in order to anticipate and optimize dynamic interactions with chosen implanted devices. In doing so, a surgeon is armed with more information during intra-operative positioning of the implanted devices and can expect more favorable patient outcomes more often. The present invention more specifically aims to solve the problems encountered by the prior art by using a means for knee prosthesis templating which is more dynamic than a static X-ray at full extension.